1. Field of the Invention
The present invention relates to an operation key assembly for performing an operation for selecting one or more keys from among a plurality of keys and for performing a key input corresponding to the operated one or more keys. More specifically, the present invention relates to an operation key assembly which enables simultaneous operation of mutually adjacent keys.
2. Description of the Related Art
Button type keys, which are pressed and operated with the fingertip, have been used as operation keys for various apparatuses such as a camera. In particular, four-direction keys, in which four button type keys are arranged in a cross-like arrangement, have been used in cameras. As one form of such conventional four-direction keys, a configuration has been known in which the upper, lower, left, and right portions of one key can be respectively and separately operated and key inputs corresponding to the four directions of up, down, left, and right-direction portions can be performed in accordance with the operated portion. In addition, as another form of such conventional four-direction keys, a configuration has been known in which a pair of up-and-down-direction keys and a pair of horizontal-direction keys, i.e., four keys in total including up, down, left, and right keys, are circumferentially arranged and a key input corresponding to the operated key can be performed by selectively operating either one of the up, down, left, and right keys. Japanese Patent Application Laid-Open No. 2003-272485 discloses a technique for the former type four-direction key, in which either one of up, down, left, and right portions of a key with an annular plate shape is depressed and tilted and a key input corresponding to the direction of the tilt can be performed. In Japanese Patent Application Laid-Open No. 06-154422 discloses an example of a three-direction key, which is one form of the latter type key including three independent keys.
In these types of four-direction keys, key inputs can be performed in four directions of up, down, left, and right. In recent years, a conventional type key has been proposed, in which two mutually adjacent keys can be simultaneously operated to enable a key input corresponding to an intermediate direction between the two operated keys. In Japanese Patent Application Laid-Open No. 2003-272485, a key input corresponding to the upper right direction can be performed by operating and pressing down an intermediate portion between up and down portions, for example, of a key with an annular plate shape, i.e., by operating and pressing down the upper right portion of the key. More specifically, key inputs corresponding to eight directions in total can be performed, including key inputs corresponding to the four directions of up, down, left, and right directions and key inputs corresponding to the four intermediate directions between them. In addition, in Japanese Patent Laid-Open No. 06-154422, by simultaneously operating two mutually adjacent keys among circumferentially arranged three keys constituting a three-direction key, key inputs corresponding to the intermediate directions between the three keys can be performed. In other words, key inputs corresponding to six directions in total can be performed.
The four-direction keys of Japanese Patent Application Laid-Open No. 2003-272485 use a technique in which operations are performed in different positions of one key with an annular plate shape. To explain this in another way, it is a technique in which the up, down, left, and right portions and intermediate portions between them are operated. Accordingly, the operation of an intermediate portion can be performed in the same manner as that for the up, down, left, or right portion. However, because the intermediate portions are not clearly distinguished or separated from the up, down, left, and right portions, the user may operate the intermediate portion by mistake when the user desires to operate the up, down, left, or right portion. On the other hand, in a technique in which two mutually adjacent keys, among a plurality of circumferentially arranged keys, are simultaneously operated to perform a key input corresponding to an intermediate direction as in the three-direction key disclosed in Japanese Patent Application Laid-Open No. 06-154422, a problem may arise with respect to the ease of operation of the simultaneous operation of the two keys. More specifically, if the interval between the two mutually adjacent keys is small, the ease of operation of the simultaneous operation of these keys increases; however, if this interval is excessively small, the user may operate a wrong key by mistake which is adjacent to the one key desired to be operated. Conversely, if the interval between the mutually adjacent keys is large, the ease of operation in selecting and operating each key increases; however, it becomes difficult to simultaneously operate mutually adjacent keys.
To address the above-described problem, Japanese Patent Application Laid-Open No. 06-154422 employs a configuration in which the interval among the three keys is small, a protrusion is provided on an operation surface of each key, the protrusion is used in singly operating the respective keys, and the keys are simultaneously operated on their flat portion in simultaneously operating mutually adjacent keys. However, in cases in which it is difficult to arrange small intervals for mutually adjacent keys, a configuration is employed in four-direction keys disposed on a back surface of a camera, particularly, in which a determination key (determination button) is provided in the center of a region of the key and four ergonomically designed keys with a shape of a small fan are circumferentially arranged around the determination key. Therefore, in such cases, it is difficult to provide a small interval between mutually adjacent keys in the circumferential direction. Therefore, if the technique of Japanese Application Patent Laid-Open No. 06-154422 is applied as it is to this type of four-direction keys for cameras, it is difficult to improve the ease of operation in simultaneously operating mutually adjacent keys.
The purpose of the present invention is to provide an operation key assembly capable of improving the ease of operation.